Back to top

Chapter 11: Organic Vegetable Production

11.1 Background

11.1.1 Organic Certification

To use a certified organic label, farming operations that gross more than $5,000 per year in organic products must be certified by a U.S. Department of Agriculture National Organic Program (NOP) accredited certifying agency. The choice of certifier may be dictated by the processor or by the target market.  A list of accredited certifiers operating in New York can be downloaded from New York State Department of Agriculture and Markets Organic Foods and Farming pages. See more certification and regulatory details under Section 11.4.1 Certification Requirements and Section 11.7: Using Organic Pesticides.

11.1.2 Organic Farm Plan

An organic farm plan is central to the certification process.  The farm plan describes production, handling, and record-keeping systems, and demonstrates to certifiers an understanding of organic practices for a specific crop.  The process of developing the plan can be very valuable in terms of anticipating potential issues and challenges, and fosters thinking of the farm as a whole system. Soil, nutrient, pest, and weed management are all interrelated on organic farms and must be managed in concert for success.  Certifying organizations may be able to provide a template for the farm plan.  The following description of the farm plan is from the NOP web site:

The Organic Food Production Act of 1990 (OFPA or Act) requires that all crop, wild crop, livestock, and handling operations requiring certification submit an organic system plan to their certifying agent and, where applicable, the State Organic Program (SOP). The organic system plan is a detailed description of how an operation will achieve, document, and sustain compliance with all applicable provisions in the OFPA and these regulations. The certifying agent must concur that the proposed organic system plan fulfills the requirements of subpart C, and any subsequent modification of the organic plan by the producer or handler must receive the approval of the certifying agent.

More details may be found at the Agricultural Marketing Service’s National Organic Program website.  The National Sustainable Agriculture Information Service, (formerly ATTRA), has produced a guide to organic certification that includes a template for developing an organic farm plan. The Rodale Institute offers a free organic transition course, which includes guidance on the certification process.

11.2 Soil Health

Healthy soil is the basis of organic farming. Regular additions of organic matter in the form of cover crops, compost, or manure create a soil that is biologically active, with good structure and capacity to hold nutrients and water (note that any raw manure applications should occur at least 120 days before harvest).  Decomposing plant materials will activate a diverse pool of microbes, including those that break down organic matter into plant-available nutrients as well as others that compete with plant pathogens on the root surface.

Rotating between crop families can help prevent the buildup of diseases that overwinter in the soil. Rotation with a grain crop, preferably a sod that will be in place for one or more seasons, deprives many disease-causing organisms of a host, and also contributes to a healthy soil structure that promotes vigorous plant growth. The same practices are effective for preventing the buildup of root damaging nematodes in the soil, but keep in mind that certain grain crops are also hosts for some nematode species.  Rotating between crops with late and early season planting dates can help prevent the buildup of weed populations. Organic growers must attend to the connection between soil, nutrients, pests, and weeds to succeed.  An excellent resource for additional information on soils and soil health is Building Soils for Better Crops, 3rd edition, by Fred Magdoff and Harold Van Es, 2010, available from SARE, Sustainable Agriculture Research and Education. For more information, refer to the Cornell Soil Health website.

Vegetable Farmers and their Sustainable Tillage Practices

11.3 Cover Crops

Unlike cash crops, which are grown for immediate economic benefit, cover crops are grown for their valuable effect on soil properties and on subsequent cash crops.  Cover crops help maintain soil organic matter, improve soil tilth, prevent erosion and assist in nutrient management. They can also contribute to weed management, increase water infiltration, maintain populations of beneficial fungi, and may help control insects, diseases and nematodes.  To be effective, cover crops should be treated as any other valuable crop on the farm, carefully considering their cultural requirements, life span, mowing recommendations, incorporation methods, and susceptibility, tolerance, or antagonism to root pathogens and other pests. Some cover crops and cash crops share susceptibility to certain pathogens and nematodes. Careful planning and monitoring is required when choosing a cover crop sequence to avoid increasing pest problems in subsequent cash crops.  Crop Rotation on Organic Farms: A Planning Manual is a valuable resource for optimizing your rotations.  See Section 11.6: Crop and Soil Nutrient Management for more information about how cover crops fit into a nutrient management plan.

A certified organic farmer is required to plant certified organic cover crop seed. If, after contacting at least three suppliers, organic seed is not available, then the certifier may allow untreated conventional seed to be used. Suppliers should provide a purity test for cover crop seed.  Always inspect the seed for contamination with weed seeds and return if it is not clean.  Cover crop seed is a common route for introduction of new weed species onto farms.

11.3.1 Goals and Timing for Cover Crops

Adding cover crops regularly to the crop rotation plan can result in increased yields of the subsequent cash crop.  Goals should be established for choosing a cover crop; for example, to add nitrogen, smother weeds, or break a pest cycle. The cover crop might best achieve some of these goals if it is in place for the entire growing season.  If this is impractical, a compromise might be to grow the cover crop between summer cash crops.  Allow two or more weeks between cover crop incorporation and cash crop seeding to permit decomposition of the cover crop, which will improve the seedbed and help avoid any unwanted allelopathic effects on the next cash crop.  Another option is to overlap the cover crop and the cash crop life cycles by overseeding, interseeding or intercropping the cover crop between cash crop rows at final cultivation.

Leaving cover crop residue on the soil surface might make it easier to fit into a crop rotation and will help to conserve soil moisture, but some of the nitrogen contained in the residue will be lost to the atmosphere, and total organic matter added to the soil will be reduced.  Turning under the cover crop will speed up the decomposition and nitrogen release from the crop residue.  Resources for determining the best cover crop for your situation include:

11.3.2 Legume Cover Crops

Legumes are the best cover crop for increasing available soil nitrogen.  Legumes have symbiotic bacteria called rhizobia, which live in their roots and convert atmospheric nitrogen gas in the soil pores to ammonium, a form of nitrogen that plant roots can use. When the cover crop is mowed, winter killed or incorporated into the soil, the nitrogen is released and available for the next crop.  Because most of this nitrogen was taken from the air, there is a net nitrogen gain to the soil.  Assume approximately 50 percent of the fixed nitrogen will be available for the crop to use in the first season, but this may vary depending on the maturity of the legume, environmental conditions during decomposition, the type of legume grown, and soil type.  For more information on legume cover crops see Chapter 8, Soil Management, Section 8.4.2, Legumes.

It is common to inoculate legume seed with rhizobia prior to planting, but the inoculant must be approved for use in organic systems. Request written verification of organic approval from the supplier and confirm this with your organic farm certifier prior to inoculating seed.

11.3.3 Non-Legume Cover Crops

Barley, rye grain, rye grass, Sudangrass, wheat, oats, and other grain crops left on the surface or plowed under as green manures or dry residue in the spring are beneficial because they capture nitrogen that otherwise might be leached from the soils. If incorporated, allow two weeks or more for decomposition prior to planting to avoid the negative impact on stand establishment from actively decomposing material. Three weeks might not be enough if soils are very cold. In wet years, the presence of cover crop residues may increase slug damage. For more information on non-legume cover crops see Section 8.5.1.

11.3.4 Biofumigant Cover Crops

Certain cover crops have been shown to inhibit weeds, pathogens, and nematodes by releasing toxic volatile chemicals when tilled into the soil as green manures and degraded by microbes, or when cells are broken down by finely chopping. Degradation is quickest when soil is warm and moist. These biofumigant cover crops include Sudangrass, sorghum-sudangrasses, and many in the brassica family. Varieties of mustard and arugula developed with high glucosinolate levels that maximize biofumigant activity have been commercialized (e.g. Caliente brands 199 and Nemat).

Attend to the cultural requirements of the cover crops to maximize growth. Fertilizer applied to the cover crops will be taken up and then returned to the soil for use by the cash crop after the cover crop is incorporated. Biofumigant cover crops like mustard should be allowed to grow to their full size, normally several weeks after flowering starts, but incorporated before the seeds become brown and hard indicating they are mature. To minimize loss of biofumigant, finely chop the tissue early in the day when temperatures are low. Incorporate immediately by tilling, preferably with a second tractor following the chopper.  Lightly seal the soil surface using a culti-packer and/or 1/2 inch of irrigation or rain water to help trap the volatiles and prolong their persistence in the soil.  Wait at least two weeks before planting a subsequent crop to reduce the potential for the breakdown products to harm the crop, also known as phytotoxicity. Scratching the soil surface before planting will release remaining biofumigant. This biofumigant effect is not predictable or consistent. The levels of the active compounds and suppressiveness can vary by season, cover crop variety, maturity at incorporation, amount of biomass, fineness of chopping, how quickly the tissue is incorporated, soil microbial diversity, soil tilth, and microbe population density.

11.4 Field Selection

For organic production, give priority to fields with excellent soil tilth, high organic matter, good drainage and airflow, manageable weed populations, and balanced nutrient levels.

11.4.1 Certification Requirements

Certifying agencies have requirements that affect field selection.  Fields cannot be treated with prohibited products for three years prior to the harvest of a certified organic crop.  Adequate buffer zones are required between certified organic and conventionally grown crops.  Buffer zones must be a barrier, such as a diversion ditch or dense hedgerow, or be a distance large enough to prevent drift of prohibited materials onto certified organic fields. Determining what buffer zone is needed will vary depending on equipment used on adjacent non-certified land.  For example, use of high-pressure spray equipment or aerial pesticide applications in adjacent fields will increase the buffer zone size.  Pollen from genetically engineered crops can also be a contaminant.  An organic crop should not be grown near a genetically engineered crop of the same species. Check with your certifier for specific buffer requirements. These buffers commonly range between 20 to 250 feet depending on adjacent field practices.

11.4.2 Crop Rotation Plan

A careful crop rotation plan is the cornerstone of organic crop production because it allows the grower to improve soil quality and proactively manage pests. Although growing a wide range of crops complicates the crop rotation planning process, it ensures diversity in crop residues in the soil, and a greater variety of beneficial soil organisms.  Individual organic farms vary widely in the crops grown and their ultimate goals, but some general rules apply to all organic farms regarding crop rotation. Rotating individual fields away from crops within the same family is critical and can help minimize crop-specific disease and non-mobile insect pests that persist in the soil or overwinter in the field or field borders.  Pests that are persistent in the soil, have a wide host range, or are wind-borne, will be difficult to control through crop rotation.  Conversely, the more host specific, non-mobile, and short-lived a pest is, the greater the potential to control it through crop rotation. The amount of time required for a crop rotation is based on the particular pest and its severity. Some particularly difficult pests may require a period of fallow.  Partitioning the farm into management units will help to organize crop rotations and ensure that all parts of the farm have sufficient breaks from each type of crop.

A well-planned crop rotation is key to weed management. Short season crops such as lettuce and spinach are harvested before many weeds go to seed, whereas vining cucurbits, with their limited cultivation time and long growing season, allow weeds to go to seed before harvest. Including short season crops in the rotation will help to reduce weed populations provided the field is cleaned up promptly after harvest. Other weed reducing rotation strategies include growing mulched crops, competitive cash crops, short-lived cover crops, or crops that can be intensively cultivated. Individual weed species emerge and mature at different times of the year, therefore alternating between spring, summer, and fall planted crops helps to interrupt weed life cycles.

Cash and cover crop sequences should also take into account the nutrient needs of different crops and the response of weeds to high nutrient levels. Excessive soil phosphorus and potassium levels can exacerbate problem weed species. A cropping sequence that alternates crops with high and low nutrient requirements can help keep nutrients in balance. The crop with low nutrient requirements can help use up nutrients from a previous heavy feeder (Table 11.4.1). A fall planting of a non-legume cover crop will help hold nitrogen not used by the previous crop. This nitrogen is then released when the cover crop is incorporated in the spring.

Rotating crops that produce abundant organic matter, such as hay crop and grain-legume cover crops, with ones that produce less, such as vegetables, will help to sustain organic matter levels and promote good soil tilth. Deep-rooted crops or cover crops in the rotation can help break up compacted soil layers.

Table 11.4.1 Crops Nutrient Requirements

Nutrient Needs of Crops
Lower Medium Higher

bean

carrot

herbs

pea

radish

cucumber

eggplant

brassica greens

pepper

pumpkin

spinach

chard

squash

winter squash

beet

broccoli

cabbage

cauliflower

corn

lettuce

potato

tomato

Adapted from Crop Rotation on Organic Farms: A Planning Manual. Charles L. Mohler and Sue Ellen Johnson, editors.

11.4.3 Pest History

Knowledge about the pest history for each field is needed to plan a successful cropping strategy. Germination may be reduced in fields with a history of Pythium or Rhizoctonia.  Avoid fields that contain heavy infestations of perennial weeds such as nutsedge, bindweed, and quackgrass as these weeds are particularly difficult to control. One or more years focusing on weed population reduction using cultivated fallow and cover cropping may be needed before organic crops can be successfully grown in those fields.  Susceptible crops should not be grown in fields with a history of Sclerotinia white mold without a rotation of several years to sweet corn or grain crops. Alternatively, treat with Contans WG™ to reduce fungal sclerotia in the soil immediately after an infected crop is harvested.

Many vegetable crops are hosts for both root-knot nematode, Meloidogyne hapla, and root-lesion nematode, Pratylenchus penetrans.   It is important to know whether or not these nematodes are present in the field in order to develop long-term crop rotations and cropping sequences that either reduce the populations in heavily infested fields or minimize their increase in fields that have no to low infestation levels.

11.4.4 Soil and Air Drainage

With the exception of powdery mildews, most fungal and bacterial pathogens need free water on the plant tissue or high humidity for several hours in order to infect. Any practice that promotes leaf drying or drainage of excess water from the root zone will minimize favorable conditions for infection and disease development.  Fields with poor air movement, such as those surrounded by hedgerows or woods, result in leaves staying wet. Plant rows parallel to the prevailing winds, which are typically in an east-west direction, and avoid overcrowding to promote drying of the soil and reduce moisture in the plant canopy.

11.5 Weed Management

Weed management can be one of the biggest challenges on organic farms, especially during the transition and the first several years of organic production. To be successful, weed management on organic farms must take an integrated approach that includes crop rotation, cover cropping, cultivation, and planting design, based on an understanding of dominant weed biology. A multi-year approach that includes strategies for controlling problem weed species in a sequence of crops will generally be more successful than attempting to manage each year’s weeds as they appear. 

Scout and develop a written inventory of weed species and severity for each field. Accurate identification of weeds is essential. Smartphone apps including iNaturalist, Pl@ntNet, and PictureThis can provide a great starting point for identification, but should be verified by extension educators or with the book, Weeds of the Northeast. Also see Cornell Weed Ecology and Rutgers Weed Gallery websites for weed fact sheets. Management plans should focus on the most challenging and potentially yield-limiting weed species in each field, being sure to emphasize options that do not exacerbate other species that are present. Alternating between early- versus late-planted, and short- versus long-season crops in the rotation can help minimize buildup of a particular weed or group of weeds with similar life cycles or growth habits, and will also provide windows for a variety of cover crops. 

11.5.2 Weed Management Methods

Planting and cultivation equipment should be set up with the same row spacing and number of rows in order to minimize crop losses and damage to crop roots during cultivation. It may be necessary to purchase specialized equipment to successfully control weeds in some crops. “Stacking,” or using more than one type of implement on a cultivator will generally improve effectiveness, especially if used in a synergistic manner (Link x). If in-row implements such as finger weeders are used, accurate steering is required, and may be achieved through belly-mounting, cultivator side-shift steering, or camera/GPS guidance systems. See resources at the end of this section to help fine-tune your weed management system. When it is an option, transplanting rather than direct seeding allows the canopy to close quicker and can reduce in-row weed development for some crops.

Planting into black plastic mulch is another strategy to improve weed control for heat-loving crops, since the mulch prevents weed germination in the area immediately near the crop. Cultivate the aisles between plastic covered beds with sweeps.  To avoid weed problems along the edges of the plastic, either use vegetable knives to under cut the margin of the plastic or use hilling discs or spider gangs to throw additional soil onto the edge of the plastic to bury weeds. These cultivations will be most effective when weeds are small.

Straw mulch is an alternative to black plastic, but will cool the soil and slow crop development. Straw can also be used for weed suppression between plastic covered beds.  Rodents may nest in the straw, however, and then feed on fruiting crops. If using straw without plastic, tine weed and/or cultivate at 10-14 day intervals until until the crop is large enough to withstand the mulching.  For effective weed control, lay 3 inches of baled compressed material or 6 inches of loose straw, which can be blown through a hydro-seeding cannon or bale chopper. Consider wider row spacings to facilitate easier application of mulch.

Resources

11.6 Crop & Soil Nutrient Management

To produce a healthy crop, soluble nutrients must be available from the soil in amounts that meet the minimum requirements for the whole plant. The total nutrient needs of a crop are much higher than just the nutrients that are removed from the field when that crop is harvested. All of the roots, stems, leaves and other plant parts require nutrients at specific times during plant growth and development. The challenge in organic systems is balancing soil fertility to supply these required plant nutrients at a time, and at sufficient levels, to support healthy plant growth. Restrictions in any one of the needed nutrients will slow growth and can reduce crop quality and yields.

Organic growers often speak of feeding the soil rather than feeding the plant. A more accurate statement is that organic growers focus their fertility program on feeding soil microorganisms rather than the plant. Soil microbes decompose organic matter to release nutrients and convert organic matter to more stable forms such as humus. This breakdown of soil organic matter occurs throughout the growing season, depending on soil temperatures, water availability and soil quality.  The released nutrients are then held on soil particles or humus making them available to crops or cover crops for plant growth.  Amending soils with compost, cover crops, or crop residues also provides a food source for soil microorganisms and when turned into the soil, starts the nutrient cycle again.

During the transition years and the early years of organic production, soil amendment with composts or animal manure can be a productive strategy for building organic matter, biological activity and soil nutrient levels. This practice of heavy compost or manure use is not, however, sustainable in the long-term.  If composts and manures are applied in the amounts required to meet the nitrogen needs of the crop, phosphorous may be added at higher levels than required by most vegetable crops. This excess phosphorous will gradually build up to excessive levels, increasing risks of water pollution or of invigorating weeds like purslane and pigweed. A more sustainable, long-term approach is to rely more on legume cover crops to supply most of the nitrogen needed by the crop and use grain or grass cover crops to capture excess nitrogen released from organic matter at the end of the season to minimize nitrogen losses to leaching (See Section 11.3: Cover Crops). When these cover crops are incorporated into the soil, their nitrogen, as well as carbon, feeds soil microorganisms, supporting the nutrient cycle. Harvesting alfalfa hay from a field for several years can reduce high phosphorus and potassium levels.

The primary challenge in organic systems is synchronizing nutrient release from organic sources, particularly nitrogen, with the crop requirements.  In cool soils, microorganisms are less active, and nutrient release may be too slow to meet the crop needs.  Once the soil warms, nutrient release may exceed crop needs. In a long-term organic nutrient management approach, most of the required crop nutrients would be in place as organic matter before the growing season starts.   Nutrients required by the crop in the early season can be supplemented by highly soluble organic amendments such as poultry manure composts or organically approved bagged fertilizer products (see Tables 11.6.4 to 11.6.7).  These products can be expensive, so are most efficiently used if banded at planting.  Pending additional rule-making, the National Organic Program states that operators using sodium nitrate shall use it in a manner that maintains or improves the natural resources of the operation, including soil and water quality, and comply with crop nutrient and soil fertility requirements. Confirm the practice with your organic certifier prior to field application.

Regular soil testing helps monitor nutrient levels, in particular phosphorus (P) and potassium (K).   Choose a reputable soil-testing lab (11.6.1) and use it consistently to avoid discrepancies caused by different soil extraction methods. Maintaining a soil pH between 6.3 and 6.8 will maximize the availability of all nutrients to plants. The Cornell Soil Health Test can help identify limiting factors in a field, suggest remediation, and if repeated over time, track improvements.

Develop a plan for estimating the amount of nutrients that will be released from soil organic matter, cover crops, compost, and manure. A strategy for doing this is outlined in Section 11.6.2: Preparing an Organic Nutrient Budget.

Table 11.6.1 Nutrient Testing Laboratories

Testing Laboratory Soil Compost/ Manure Forage
Waypoint Analytical   x  
Penn State Ag  Analytical Services Lab x x  
Dairy One x   x
University of Massachusetts: Soil and Plant Nutrient Testing Laboratory x x  

11.6.1 Fertility Requirements

Recommendations from individual crop chapters provide crop nutrient requirements. These recommendations are based on the total needs of the whole plant and assume the use of synthetic fertilizers. Farmer and research experience suggests that lower levels may be adequate in organic systems.  Nitrogen needs are not included because levels of available N change in response to soil temperature and moisture, N mineralization potential, and leaching. As many of the nutrients as possible should come from cover crop, manure, and compost additions in previous seasons.

If the crop is grown with plastic mulch, the nitrogen level can be reduced.  The more uniform moisture and warmer temperatures under plastic mulch increase the decomposition rate of soil organic matter, which increases available N.

The source of these nutrients depends on soil type and historic soil management. Some soils are naturally high in P and K, or have a history of manure applications that have resulted in elevated levels.  Additional plant available nutrients are supplied by decomposed soil organic matter or through specific soluble nutrient amendments applied during the growing season in organically managed systems. Many types of organic fertilizers are available to supplement the nutrients supplied by the soil.  ALWAYS check with your certifier before using any product to be sure it is approved.

11.6.2 Preparing an Organic Nutrient Budget

Insuring an adequate supply of nutrients when the crop needs them requires careful planning. Developing an organic nitrogen budget can help estimate the amount of nutrients released by various organic amendments as well as native soil organic matter.  Table 11.6.4 estimates common nutrient content in animal manures; however actual compost and manure nutrient content should be tested just prior to application.  Analysis of other amendments, as well as cover crops, can be estimated using published values. Keeping records of these nutrient inputs and subsequent crop performance will help evaluate if the plan is providing adequate fertility during the season to meet production goals.

Remember that with a long-term approach to organic soil fertility, the N mineralization rates of the soil will increase. This means that more N will be available from organic amendments because of increased soil microbial activity and diversity. Feeding these organisms different types of organic matter is essential to building this type of diverse biological community and ensuring long-term organic soil and crop productivity. Consider submitting soil samples for a Cornell Soil Health Test. This test includes an estimate of nitrogen mineralization rate, which indicates the potential for release of N from soil organic matter.  Testing soils over time can be useful for monitoring changes in nitrogen mineralization rate during the transition, and over time, in organic production.

Estimating total nutrient release from the soil and comparing it with soil test results and recommendations requires record-keeping and some simple calculations. Table 11.6.2 below can be used as a worksheet for calculating nutrients supplied by the soil compared to the total crop needs.

Table 11.6.2 Calculating Nutrient Credits and Needs

  Nitrogen (N) lbs/acre Phosphate (P2O5) lbs/acre Potash (K2O) lbs/A
1. Total crop nutrient needs      
2. Recommendations based on soil test      
3. Credits      
   a.  Soil organic matter      
   b.  Manure      
   b.  Compost      
   c.  Prior cover crop      
4. Total credits:      
5. Additional needed (2-4) =      

Line 1. Total Crop Nutrient Needs: Using cucurbits as an example, research indicates that an average cucurbit crop requires 100 lbs. of available nitrogen (N), 120 lbs. of phosphorus (P), and 120 lbs. of potassium (K) per acre to support a medium to high yield.

Line 2. Recommendations Based on Soil Test: Use Table 11.6.3 (from Section 17.3) to determine the amount of P and K needed based on soil test results.

Table 11.6.3 Recommended Amounts of Phosphorus and Potassium for Cucurbits Based on Soil Tests

  Soil Phosphorus Level Soil Potassium Level
  P2Olbs/A  <K2O lbs/A
Level shown in soil test low med high low med high
Total nutrient recommendation 120 80 40 120 80 40

Line 3a. Soil Organic Matter:  Using the values from your soil test, estimate that 20 lbs. of nitrogen will be released for each percent organic matter in the soil.

Line 3b. Manure: Assume that manure will release N for 3 years. Based on the test of total N in the manure applied, estimate that 50% is available in the first year, and then 50% of the remaining is released in each of the next two years.  For an application rate of 100 lbs. of N as manure, 50 lbs. would be available the first year, 25 lbs. in year 2, and 12.5 lbs. in year 3.  Remember, any raw manure applications must occur at least 120 days before harvest of a vegetable crop.

Line 3c. Compost: Estimate that 10 to 25% of the N contained in compost will be available the first year.  Compost maturity will influence how much N is available.  If the material is immature, more of the N may be available to the crop in the first year.  A word of caution: Using compost to provide for a crop’s nutrient needs is not generally a financially viable strategy. The total volume needed can be very expensive for the units of N available to the crop. Most stable composts should be considered as soil conditioners, improving soil health, microbial diversity, tilth, and nutrient retaining capacity. Any compost applied on organic farms must be approved for use by your farm certifier. Compost generated on the farm must follow an approved process outlined by your certifier.

Line 3d. Cover Crops: Consult the cover crop resources listed in section 11.3 to estimate the amount of N fixed by legume cover crops. Estimate that 50 percent of the fixed N is released for plant uptake in the current season.

Line 4. Total Credits: Add together the various N values from the organic matter, compost and cover crops to estimate the N supplying potential of the soil (see example below). There is no guarantee that these amounts will actually be available in the season, since soil temperatures, water, and crop physiology all impact the release and uptake of these soil nutrients. If the available N does not equal the minimum requirement for this crop (~90 lbs/acre), a sidedress application of organic N may be needed. There are several sources for N for organic sidedressing (see Table 11.6.5) as well as pelleted composts.  Early in the organic transition, a grower may consider increasing the N budget supply by 30%, to help reduce some of the risk of N being limiting to the crop.

Table 11.6.4 includes general estimates of nutrient availability for manures and composts but these can vary widely depending on animal feed, management of grazing, the age of the manure, amount and type of bedding, and many other factors. Manure applications may not be allowed by your certifier or marketer even if applied 120 days before harvest.

Table 11.6.4 Nutrient Content of Common Animal Manures and Manure Composts

  Total  N P2O5 K2O N1 1 N2 2 P2O5 K2O
  Nutrient content lb/ton Available nutrients lb/ton in first season
Dairy (with bedding) 9 4 10 6 2 3 9
Horse (with bedding) 14 4 14 6 3 3 13
Poultry (with litter) 56 45 34 45 16 36 31
Composted dairy manure 12 12 26 3 2 10 23
Composted poultry manure 17 39 23 6 5 31 21
Pelleted poultry manure  3 80 104 48 40 40 83 43
Swine (no bedding) 10 9 8 8 3 7 7
  Nutrient content lb/1000 gal. Available nutrients lb/1000 gal first season
Swine finishing (liquid) 50 55 25 25a 20b 44 23
Dairy (liquid) 28 13 25 14a 11 b 10 23

1N1 is an estimate of the total N available for plant uptake when manure is incorporated within 12 hours of application,  2N2 is an estimate of the total N available for plant uptake when manure is incorporated after 7 days. 3Pelletized poultry manure compost. (Available in New York from Kreher’s.)

a injected, b incorporated.  Adapted fromUsing Manure and Compost as Nutrient Sources for Fruit and Vegetable Cropsby Carl Rosen and Peter Bierman and Penn State Agronomy Guide.

Table 11.6.5 Available Nitrogen in Organic Fertilizer

  Pounds of Fertilizer/Acre to Provide X Pounds of N per Acre
Sources 20 40 60 80 100
Blood meal, 13% N 150 310 460 620 770
Soy meal 6% N (x 1.5)a, also contains 2% P and 3% K2O 500 1000 1500 2000 2500
Fish meal 9% N, also contains 6% P2O5 220 440 670 890 1100
Alfalfa meal 2.5% N also contains 2% P and 2% K2O 800 1600 2400 3200 4000
Feather meal, 15% N (x 1.5)a 200 400 600 800 1000
Chilean nitrate 16% N cannot exceed 20% of crop’s need. 125 250 375 500 625

See information under table 11.6.7

Table 11.6.6 Available Phosphorous in Organic Fertilizers.

  Pounds of Fertilizer/Acre to Provide X Pounds of P2O5 Per Acre
Sources 20 40 60 80 100
Bonemeal 15% P2O5 130 270 400 530 670
Rock Phosphate 30% total P2O5 (x4)a 270 530 800 1100 1300
Fish meal, 6% P2O5 (also contains 9% N) 330 670 1000 1330 1670

See information under table 11.6.7

Table 11.6.7 Available Potassium in Organic Fertilizers

  Pounds of Fertilizer/Acre to Provide X Pounds of K2O per acre:
Sources 20 40 60 80 100
Sul-Po-Mag 22% K2O also contains 11% Mg 90 180 270 360 450
Wood ash (dry, fine, grey) 5% K2O, also raises pH 400 800 1200 1600 2000
Alfalfa meal 2% K2O also contains 2.5% N 1000 2000 3000 4000 5000
Greensand or Granite dust  1% K2O (x 4) a 8000 16000 24000 32000 40000
Potassium sulfate 50% K2O 40 80 120 160 200

a Application rates for some materials are multiplied to adjust for their slow to very slow release rates. Tables 11.6.5 – 11.6.7 adapted by Vern Grubinger from the University of Maine soil testing lab.

An example of how to determine crop nutrient needs.

You will be growing an acre of winter squash. The Cornell Integrated Crop and Pest Management Guidelines suggests a total nutrient need for a cucurbit crop is 100 lb. N, 120 lb. P, and 120 lb K per acre for a high yielding crop.  Soil tests show a pH of 6.5, with medium P and low K levels and recommends 80 lbs P205/acre and 120 lbs K20/acre (see Table 11.6.4).  The field you’ll be planting has 2% organic matter and there is a stand of red clover that will be turned in a week or so prior to planting (see resources listed in section 11.3). Last season you injected 1000 gallons per acre of liquid hog manure into the red clover stubble after taking the last cutting of hay.

Table 11.6.8 Example: Calculating Nutrient Credits and Needs Based on Soil Sample Recommendations

  Nitrogen (N) lbs/A Phosphate (P2O5) lbs/A Potash (K2O) lbs/acre
1. Total crop nutrient needs: 100 120 120
2. Recommendations based on soil test # not provided 80 120
3.  Credits      
   a.  Soil organic matter 2% 40 --- ---
   b.  Manure – 1000 gal hog 25 44 23
   c.  Compost - none 0 0 0
   d.  Cover crop – red clover 50 0 0
4. Total credits: 115 44 23
5. Additional needed     (2-4) = 0 36 97

Table 11.6.4 indicates about 25 lbs. N will be released in the first season from 1000 gallons of hog manure injected.  Estimate that each percent organic matter will release about 20 lbs. of N, so the 2% soil organic matter will supply 40 lbs. N (line 3a).  Consulting the Northeast Cover Crops Handbook, we estimate that the red clover cover crop will release about half its fixed N, or 50 lbs. as it decomposes (line 3d), for a total estimated N released and available for plant uptake of 115 lbs. per acre.  The 44 lbs. of P released from the injected manure will need to be supplemented by an additional 40 lbs P through applying ~250 lbs/A of bonemeal (Table 11.6.6) to meet the soil test recommendation of 80 lbs per acre. Potassium will also need to be supplemented in this example. The manure supplies 23 of the 120 lbs. needed. The remaining ~100 lbs. K2O/acre, can be incorporated through broadcasting 200 lbs. of potassium sulfate from an organically approved product, if soil tests indicate sufficient magnesium. If magnesium is needed, then apply ~450 lbs. of Sul-Po-Mag per acre (Table 11.6.7).

11.7 Using Organic Pesticides

Given the high cost of many pesticides and the limited amount of efficacy data from replicated trials with organic products, the importance of developing an effective system of cultural practices for insect and disease management cannot be emphasized strongly enough.  Pesticides should not be relied on as a primary method of pest control.    Scouting and forecasting are important for detecting symptoms of diseases at an early stage. When conditions do warrant an application, proper choice of materials, proper timing, and excellent spray coverage are essential.

11.7.1 Sprayer Calibration and Application

Calibrating sprayers is especially critical when using organic pesticides since their effectiveness is sometimes limited. For this reason, they tend to require the best spraying conditions to be effective. Read the label carefully to be familiar with the unique requirements of some products, especially those with live biological organisms as their active ingredient (e.g. Contans WG). The active ingredients of some biological pesticides (e.g. Serenade and Sonata) are actually metabolic byproducts of the organism.  Calculating nozzle discharge and travel speed are two key components required for applying an accurate pesticide dose per acre.  Applying too much pesticide is illegal, can be unsafe, and is costly whereas applying too little can fail to control pests or lead to pesticide resistance.

Resources

11.7.2 Regulatory Considerations

Organic production focuses on cultural, biological, and mechanical techniques to manage pests on the farm, but in some cases pesticides, which include repellents, allowed for organic production are needed.  See NYS DEC’s Bureau of Pest Management - Information Portal for pesticides currently registered for use in NYS.  Additional products may be available for use in other states.

To maintain organic certification, products applied must also comply with the National Organic Program (NOP) regulations as set forth in 7 CFR Part 205, sections 600-606. The Organic Materials Review Institute (OMRI) is one organization that reviews products for compliance with the NOP regulations and publishes lists of compliant products, but other entities also make product assessments. Organic growers are not required to use only OMRI listed materials, but the list is a good starting point when searching for allowed pesticides.

Finally, farms grossing more than $5,000 per year and labeling products as organic must be certified by a NOP accredited certifier who must approve any material applied for pest management. ALWAYS check with the certifier before applying any pest control products.  Some certifiers will review products for NOP compliance.

Note that "home remedies" may not be used. Home remedies are products that may have properties that reduce the impact of pests. Examples of home remedies include the use of beer as bait to reduce slug damage in strawberries or dish detergent to reduce aphids on plants. These materials are not regulated as pesticides, are not exempt from registration, and are therefore not legal to use.

Do you need to be a certified pesticide applicator? The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) defines two categories of pesticides: general-use and-restricted use. NYS DEC also defines additional restricted-use pesticides. Pesticide applicator certification is required to purchase and use restricted-use pesticides. Farmers who purchase and use only general-use pesticides on property they own or rent do not need to be certified pesticide applicators. However, we do encourage anyone who applies pesticides to become certified.

Worker Protection Standard training. If the farm has employees who will be working in fields treated with a pesticide, they must be trained as workers or handlers as required by the federal Worker Protection Standard (WPS). Having a pesticide applicator certification is one of the qualifications needed to be a WPS trainer. Certified pesticide applicators meet the WPS training requirements. For more information on the Worker Protection Standard see How To Comply with the Worker Protection Standard (Link 67). Find more information on pesticide applicator certification from the list of State Pesticide Regulatory Agencies or, in New York State, see the   Cornell Pesticide Management Education Program website.

11.7.3 Pollinator Protection

Honey bees, wild bees, and other insects are important for proper pollination of many crops. Poor pollination results in small or odd-shaped fruit as well as low yields.

To avoid harming bees with insecticides, remember these general points:

  • Always read the label before use.
  • Do not spray blooming crops.
  • Mow blooming weeds before treatment or spray when the blossoms are closed.
  • Avoid application during the time of day when bees are most numerous.
  • Make application in the early morning or evening.

If pesticides that are highly toxic to bees are used in strict accordance with label directions, little or no harm should be done to bees. Label statements on pesticides that are highly toxic to honey bees may carry a caution statement such as: “This product is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees are visiting the treatment area.”

In early 2015 the EPA proposed new pollinator protection label language to protect managed bees under contract pollination services. The intent of this new language is to protect bees from contact exposure to pesticides that are acutely toxic to bees. Once the new language is finalized, pesticide labels will include the new wording and requirements. As part of this proposal, EPA identified certain active ingredients that are acutely toxic to bees. For more information on pollinator protection, visit  the EPA Protecting Bees and Other Pollinators from Pesticides and Pesticide Environmental Stewardship: Pollinator Protection

11.7.4 Optimizing Pesticide Effectiveness

Information on the effectiveness of a particular pesticide against a given pest can sometimes be difficult to find.  Some university researchers include pesticides approved for organic production in their trials; some manufacturers provide trial results on their web sites; some farmers have conducted trials on their own. The Resource Guide for Organic Insect and Disease Management  and Cornell organic crop production guides provide efficacy information for many approved materials.

In general, pesticides allowed for organic production may kill a smaller percentage of the pest population, could have a shorter residual, and may be quickly broken down in the environment. Read the pesticide label carefully to determine if water pH or hardness will negatively impact the pesticide’s effectiveness. Use of a surfactant may improve organic pesticide performance. Search the OMRI products list for NOP-compliant adjuvants.  Regular scouting and accurate pest identification are essential for effective pest management.  Thresholds used for conventional production may not be useful for organic systems because of the typically lower percent mortality and shorter residual of pesticides allowed for organic production. When pesticides are needed, it is important to target the most vulnerable stages of the pest. Thoroughly cover plant surfaces, especially in the case of insecticides, since many must be ingested to be effective. The use of pheromone traps or other monitoring or prediction techniques can provide an early warning for pest problems, and help effectively focus scouting efforts.

Maintained by Abby Seaman, New York State IPM Program. Last modified 2020.